Alternatives to Cams - Illegal Red Light Cameras

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FAQ # 6

Alternatives to Cameras
Updated 8-29-07

Engineers who have studied red light running - those who do not stand to gain financially from the use of red light cameras - suggest that cities try alternatives to cameras before installing cameras. Why is that, and what are the alternatives?

Part (A) of Answer: One alternative is to lengthen the yellow light, which is known to dramatically reduce the number of cars running the lights. One study (at page 67) showed a 69% decrease in violations when a yellow was increased from 4.0 seconds, to 4.5 seconds. Other studies give similar results, and also rated engineering countermeasures such as longer yellows "most effective" in reducing unintentional running while enforcement, including cameras, was considered "less effective."

Follow-up Question # 1: Won't drivers get used to the longer yellows, and keep running them?

Answer to Follow-up # 1: No, drivers do not adjust, and the violations stay down. Numerous sources confirm that. Here are some -

One real world example comes from Fairfax County, Virginia. This graph, from the first study cited above, shows the long-term effect of increased yellows.

Another real world example comes from Mesa, Arizona. Mesa increased left-turn yellows from three seconds to four seconds at six photo enforced intersections, saw an immediate 2/3 (or more) drop in the number of violators at each intersection - which stayed down in the 4+ years after the change. See the before-and-after figures at: City of Mesa Documents.

Internal documents from the City of San Diego show numerous intersections rejected as camera sites, with the notation, "long yellow - vio(lation) volume not there" - an Industry acknowledgment that at intersections with longer yellows, there will not be enough violations to make the system pay.

See also the discussion of this question, by traffic engineers, in the Electronic National Dialog on Transportation Operations, at: http://www.ntoctalks.com/opdialog/index.cgi?read=381 . The following is a portion of that discussion.

"It has frequently been claimed that if the yellow is 'too long,' more drivers will use part of the yellow as green. More drivers - it was argued - would cross after yellow onset with long than with short yellow."
"The data show that the percentage of last-to-cross vehicles clearing the intersection (T+0.2) seconds or more past the yellow onset was not appreciably changed by the extension of the yellow phase." ["The Influence of the Time Duration Of Yellow Traffic Signals On Driver Response," Stimpson/Zador/Tarnoff, ITE Journal, November 1980]

"Research has consistently shown that drivers do not, in fact, adapt to the length of the yellow." [Determining Vehicle Change Intervals - A Proposed Recommended Practice", ITE, 1985]

"Olson and Rothery reported in 1972 that their research showed that drivers were 'virtually' certain to stop if their required deceleration rate was less than 8 feet per second squared [ 0.25 G ] and virtually certain to continue if the deceleration rate required was in excess of 12 feet per second squared [ 0.38 G ]." [Determining Vehicle Change Intervals - A Proposed Recommended Practice", ITE, 1985]

Follow-up Question # 2: OK, running goes down (and stays down) when you lengthen the yellow, but do accidents also go down?

Answer to Follow-up # 2: Lengthening the yellow also reduces severe accidents. One source is a 2004 study by the Texas Transportation Institute which found (at page 2-20, see graph below), "…an increase in the yellow duration of 1.0 second is associated with an MF [crash frequency] of about 0.6, which corresponds to a 40 percent reduction in crashes."

Another source is more from the Electronic National Dialog: "The average implied deceleration rate of the group with the highest crash rate was slightly over 13 feet per second squared [ 0.41 G ], and the deceleration rate for the group with the lowest crash rate was 8.5 feet per second squared [ 0.27 G ]." ["Effect of Clearance Interval Timing on Traffic Flow and Crashes at Signalized Intersections," Zador/Stein/Shapiro/Tarnoff, ITE Journal, November 1985]

Part (B) of Answer: Another alternative is to improve street markings. 2005 research sponsored by the Florida Department of Transportation concluded (at page 69) that improving street markings near intersections would reduce red light running by up to 74 percent. Engineering countermeasures such as better markings are rated "most effective" in reducing unintentional running whereas enforcement, including cameras, is considered "less effective."

A couple more engineering countermeasures are larger signal lamps (12" dia. instead of 8") and, where there is no signal light on the "near side" of the intersection, adding one.

Conclusion

Most people who intentionally run signals do so by just a small fraction of a second. On the other hand, a search through the accident photos (captured by ticket cameras) that the Industry has posted on the 'net yields, almost exclusively, photos of accidents which occurred many seconds after the light turned red - accidents that most likely were caused by unintentional running. (Who would deliberately run a signal by the ten or twenty seconds shown on many of the Industry's photos?) The preponderance of photos with long red times among the Industry's crash photos argues that unintentional running is more dangerous than intentional running. Engineering countermeasures such as longer yellows and better markings are more effective against unintentional running than is enforcement.

Among the advantages of doing the alternatives above (engineering countermeasures) are -

(1) A reduction of red light running by ALL drivers, including visitors to town and unintentional runners - not just the "locals" who know that there are cameras around.

(2) A statistically significant decrease in the number of severe accidents without a "side-effect" increase in rear-end accidents. (For more about rear-enders, see FAQ # 19.)

(3) These alternatives are cheap, so can be done on all problematic intersections in town, not just a few.

(4) Fixing the problematic intersections - rather than maintaining the status quo and taking pictures - helps to protect the city against liability claims arising from accidents.